Research On The Relationship Between The Elastic Wave Velocity And Intensity Of The Concrete Beams Under Repeated Load

It is an urgent task to make a fatigue and health diagnosis for the concrete beamsthat are withstanding frequently repeated load, which has great significance forengineering safe operation.Concrete is a multiphase inhomogeneous body that is made up of a variety ofmaterials. For normal concrete, in which the propagation speed of sound wave is in acertain range. When the wave meets a defect in the propagation path, such as faults,fractures, mud and segregation, etc., it will diffract and its velocity will slow down,which will lead to a waveform distortion, delay the reach of measuring points’fluctuations, reduce its amplitude, etc. With these changes of acoustic parameters ofultrasonic wave propagating in the concrete, we can analyze and judge the internalsituation of concrete.This paper use different intensities repeat loading concrete structures fatigue testmethods to expand research on the correlation between the elastic wave velocity andstrength degradation of concrete structures under repeated load. This article doesfatigue strength test on six concrete beams, which are the same at materials,reinforcement ratio, sand ratio, water ratio and curing environment. According to thetesting requirements, we suspend the repeated load for30minutes after times of fiftythousand, one hundred thousand, one hundred and fifty thousand, two hundredthousand, three hundred thousand, four hundred thousand, six hundred thousand, eighthundred thousand, one million, one and half million, two million and signs of damageoccurs. When the fatigue testing machine stabilizes at a certain level of load, wemeasure the crack width, deflection and elastic wave velocity of the concrete beammembers.On the basis of the above experiments, this article studies law of correspondencebetween deformation and progressive damage of concrete beam members and thenumber of repeated load, and we also research on correspondence between elasticwave velocity distribution and velocity variation of concrete beam members and thenumber of repeated load, and also the experimental relationship among load repetitions, fatigue state and elastic wave velocity variation of concrete structures. Onthis basis, according to the strength degradation law, we have initially established amonitoring and evaluation method for durable elastic wave velocity of concretebeams——In accordance with the damage severity of concrete under repeated load,the health status of the concrete is divided into four grades: intact, basically intact,minor damage and serious injury——which lays the foundation for the concrete’shealth diagnosis and life prediction. This series monitoring and evaluation methodsand research ideas can provide reference for health diagnosis and life evaluation ofconcrete bridge structures.